The present invention relates to a semiconductor device used, for example, in a high frequency band.
A microwave power amplifier using semiconductor device for the high frequency (hereinafter referred to as HF) band, using a gallium arsenide field effect transistor (hereinafter referred as GaAsFET), for example, is assembled in a package which is so constructed that a frame-shaped metallic sidewall is provided on a base plate, an opening formed by the sidewall on an upper portion is covered with a metallic lid. In this package, an input matching circuit is arranged on an input side of the GaAs FET and an output matching circuit is arranged on an output side of the GaAs FET. These matching circuits are formed on a dielectric plate fixed on the base plate.
A part of the metallic sidewall adjacent to the input matching circuit is composed of an insulator such as ceramic and a band-shaped conductor for an input signal is provided penetrating through the sidewall formed by the insulator. One end of an input lead wire, which is lead out from the package, is connected with one end of the band-shaped conductor. A wire, which is connected with an input end of the input matching circuit in the package, is connected with the other end of the input band-shaped conductor by bonding.
A part of the metallic sidewall adjacent to the output matching circuit is similarly composed of an insulator and a band-shaped conductor for an output signal is provided penetrating through the sidewall formed by the insulator. One end of an output lead wire, which is lead out from the package, is connected with one end of the band-shaped conductor for an output signal. A wire, which is connected with an input end of the input matching circuit in the package, is connected with the other end of the input band-shaped conductor by bonding.
The output end of the input matching circuit is connected to the input end of the GaAs FET by wire bonding and the output end of the GaAsFET is connected to the input end of the output matching circuit by wire bonding. In the microwave power amplifier thus composed, input signals received by the input lead wire is supplied to the input end of the input matching circuit inside the package via input band-shaped conductor. Input signals, converted by the input matching circuit are supplied to the input end of the GaAsFET to be amplified. Output signals from the GaAsFET are lead out of the package via output matching circuit and the output band-shaped conductor, and are outputted through the output lead wire.
Such microwave power amplifier is disclosed, for example, in Japanese patent disclosure H9-153839.
Recently, a demand is arising for a high output power for such conventional semiconductor device as disclosed above. Consequently, durability of the band-shaped conductor, which penetrates through the sidewall portion of the package, against interrupting with a high current is required. Namely capability to a high current interrupting is required. To achieve the tolerance to a high current interrupting, there is a method for increasing a thickness of the band-shaped conductor, for example. However, if the thickness of the band-shaped conductor is increased, following problems arise.
The band-shaped conductor penetrating through the sidewall portion is sealed by a pair of insulator members such as ceramic members, for example, provided on and under the band-shaped conductor jointly forming a portion of the sidewall. Therefore, joining of the pair of ceramic members becomes difficult and hermetic seal of the portion where the band-shaped conductor is penetrating is degraded, if the thickness of the band-shaped conductor is increased. As the result, it becomes difficult to keep air tightness of the package in which the semiconductor elements and other elements are sealed. For the above reasons, there exists a limit in the thickness of the band-shaped conductor.
There is another method to achieve the capability to a high current interrupting, in which a width of the band-shaped conductor, namely a width of a pattern is broadened, for example. To make the width of the pattern broad, the thickness of the sidewall portion between the band-shaped conductor and the surface of the baseboard, made of the ceramic, for example, should be made thicker in order to keep predetermined impedance. When the ceramic is made thicker, difference in the height becomes great between the circuit pattern composing the input matching circuit or output matching circuit and the band-shaped conductor. As the result, wires connecting circuit pattern and band-shaped conductor become long in vertical direction, for example, radiation loss increases. Further, if difference in the height becomes large between circuit pattern and band-shaped conductor, problems arise that a discontinuity arises in the path of HF current and reflection occurs at the portion.